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Something's lying to me

I went on a ride today to test out my new lowered Wilber shocks on the R1100RS. Bike handled great, went into corners nice, felt more confident. Now the issue. I noticed while in 5th gear that the tach and speedo were in sync (same place on the dial in relation to each other) When I was on the freeway, gear lever said it was in 5th, play in lever, but tach was at 5K and speedo was at 70. Something is off, can the tach be lying or is it more serious??
Since I messed with the center stand I first thought that may be cause, but everything clears with no issue. When I down shift, it goes into every gear with a corresponding jump in RPM. Drop from 5th to 4th, pretty small in tach jump. Last time I rode before this, there was some hesitation in going into 5th and the proper tach drop.
My tranny is the M93.

Off

Did it seem like you were going very fast like 80 or 90 mph. I ONCE RECIEVED A FRIENDLY REMINDER FROM A ILLINOIS STATE TROOPER that 85 or so was to fast in a 55 zone I did not think I was going that fast but knew I was well over 55 so started paying attention noticed spedo a little bit erratic so went 3500 in 5th which should put me at 60 or in that neighborhood and speed showed 60 sometimes and sometimes 40!
Bike 1994 R1100RS about 68,ooo miles got new speedometer and cable installed and things went back to normal.
Before installing new stuff I took a drill and old speedometer cable compared old and new speedometer and it seemed like there was some wear in old speedometer where socket cable goes in letting it slip sometimes.
New spedo about $125 much cheaper than I thought it would be ( new stuff cost about the same as ticket)

If I was going 5K in 5th gear I think I would be going in the neighborhood of 100 MPH. I was a little faster than the traffic, but not that much faster. I pulled the tank and side covers, got all the panels off to pull the speedo cable, looked really nice, no abnormal wear of any kind, nice square drive end. Lay down next to shifter, cannot see anything that indicates restricted movement.
something has to be amiss, can you get into a false 5th, where you are not really into the gear? If I remember correct 80 was about 3750 RPM so this 70 at 5K just doesn't make much sense.

Still off

I assume Nevada interstates have mile markers like ours do if so do some timed miles or if they put out the radar speed warning things before construction zones you can use them to get actual speed or close to it.

If speed and tach both right that sounds like bike in 3rd my bike gets cranky at times if you don't let shifter go all the way down than preload it does not always shift, also my gear position indicator very erratic, also at those rpm should be able to do a clutchless upshift very easily ( keep some upward pressure on shifter and roll off throttle at right rpm will shift up if not in 5th)

I assume Nevada interstates have mile markers like ours do if so do some timed miles or if they put out the radar speed warning things before construction zones you can use them to get actual speed or close to it.

Primary Reduction

Still wondering about the misinformation I am receiving on the speed/rpm question. I have now a GPS app on my iPhone to determine speed, had to buy a holder to mount the phone on my RS. If weather cooperates I may check it today. I seriously doubt the speedo is the issue as I was riding a know route up a mountain, my indicated speed was within the range I usually go up that road.

I was doing some calculations on speed as determined by RPM, gear ratios, tire size and such. Our BMWs have a primary reduction in the system which will affect the calculations. On my bike the 5th gear is .829, rear end is 3.091 but I have a primary reduction of 1.591, so does one multiply that by the tranny gear ratio to get a correct figure for the calculation?

When I first did the calcs, without the reduction my speed at 5K would have been 145MPH, with the reduction figured ( 1.591x.827= 1.31) it was in the 90s which seem more logical. When I was determining speed in gears, being in 3rd gave me the closest condition to the 70MPH at 5K rpm I was seeing on my last ride when everything said I was in 5th.

Still wondering about the misinformation I am receiving on the speed/rpm question. I have now a GPS app on my iPhone to determine speed, had to buy a holder to mount the phone on my RS. If weather cooperates I may check it today. I seriously doubt the speedo is the issue as I was riding a know route up a mountain, my indicated speed was within the range I usually go up that road.

I was doing some calculations on speed as determined by RPM, gear ratios, tire size and such. Our BMWs have a primary reduction in the system which will affect the calculations. On my bike the 5th gear is .829, rear end is 3.091 but I have a primary reduction of 1.591, so does one multiply that by the tranny gear ratio to get a correct figure for the calculation?

When I first did the calcs, without the reduction my speed at 5K would have been 145MPH, with the reduction figured ( 1.591x.827= 1.31) it was in the 90s which seem more logical. When I was determining speed in gears, being in 3rd gave me the closest condition to the 70MPH at 5K rpm I was seeing on my last ride when everything said I was in 5th.

It sounds to me like the transmission was in 3rd gear.

Paul Glaves - "Big Bend", Texas U.S.A
"The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russellhttp://web.bigbend.net/~glaves/

Paul, that's what I am thinking even though when I down shifted it behaved as if I had been in 5th. Been analyzing changes that occured prior to me having this issue. I installed lowered (30mm) shocks on bike, I also lowered the center and side stand. My thinking is that the positioning the lift arm on the center stand has caused my foot to change position as everything is an inch more forward, which may be affecting my ability to lower the foot enough to allow the shifter to reset for the next up cog. I have adjusted the shifter linkage and taken it up one turn which should raise the lever to give me more foot room underneath. It's clearing up nicely and the temps will be in the low 50s, will see if my theory is correct.

Went for a short ride on the freeway to see what was up, still was hitting the 70mph 5K RPM relation in what appeared to be 5th. Did the speedo test and there was a slight variation, I was in traffic so I couldn't hit higher speeds, plus I didn't want to rear end a car while I was trying to see the iPhone face. When I was coming home and taking it through the gears I did start getting some indications where the speedo was ahead of the tach on the face to face relation of the needles. I may pull the center stand off and try again to see if it is fouling the lever in any way. Testing it in the shop doesn't show it is hitting, but the bracket that has the stop bumper on it is sure close to the gear lever, there is enough wiggle in the lever that it may be hitting it.

Maybe the tach is lying

Removed the center stand to once and for all to eliminate that as a source interfering with my shifting. Went on freeway and nothing had changed, still running 70 MPH at 5K in 5th gear. Now it is down to the tach or the BIG fear, the tranny. Ordered one of those induction tachometers just to validate the tach is the issue.

If you replaced both shocks did you R&R the front wheel? The front wheel speedo drives on that vintage R1100 tend to start having issues as the miles accumulate, and have been known to seize completely. Plus, it is very easy to incorrectly engage the drive tabs as the wheel is inserted, or to put the locating tabs on the speedo drive in the wrong orientation. The latter leaves the speedo cable pointing downward as it exits the drive unit, putting a too-sharp bend on the speedo cable that can interfere with correct speedo function and lead to cable breakage. Before you start worrying about clutch and tranny you might want to check that speedo drive. A slipping clutch or tranny is usually noticeable enough to be a clear and distinctive issue.

Looks like a bad tachometer

Received the induction tachometer a few minutes ago. Ran out to garage hooked it up and fired bike up. It read lower than OEM at lower RPM ranges, when run up to 4K then 5K the induction model was reading lower by 1000 RPM or more, difference grew as I increased RPM. Difference is large enough to point to bad OEM tachometer.

Received the induction tachometer a few minutes ago. Ran out to garage hooked it up and fired bike up. It read lower than OEM at lower RPM ranges, when run up to 4K then 5K the induction model was reading lower by 1000 RPM or more, difference grew as I increased RPM. Difference is large enough to point to bad OEM tachometer.

Thanks, in a way I was relieved to find the fault was the tach and it not being any issue with the transmission. Pulled the tach today, made in the UK, by Luc---? Can't quite make it out. Date code 3/27/93.
Ordered a new unit from A&S cycle.